Then why was Transformers so nationally-loved? Wasn't it also a story about aliens?

Beats me.

Strangely though, I don't think the fantasy genre ever received a similar treatment by the Indonesian so-called "movie-goers". Lord of the Rings was a huge success here, though I bet only a few can remember the characters names after they left the theatre. Harry Potter and Twilight too. I think it's more or less the same with the superhero genre, and that even contains characters that are freakier than your average alien.

If people can relate with a boy with lightning-shaped scar on his forehead; or a sparkling emo vampire; or a group of people setting off on a journey to throw a ring into a volcano, then why is it so hard for them to relate to a laser sword-wielding warrior-monk? Or a robot sent to the past to kill the mother of a future resistance leader?

There's nothing wrong with an out-of-this-world movie experience once in a while, no?